According to the information recorded on the Doegen speaker questionnaire in September 1931, John Neddy Maguire was born in the parish of Glangevlin in the west of County Cavan in June 1849. Both parents were from Glangevlin, and his father was a farmer. In response to questions, the speaker stated that he spent all his childhood and adult life in Glangevlin, and had attended primary school at Tullycasson. His own occupation was as a farmer. Irish was his mother language until the age of seven, and he could also speak English. He could read and write English but not Irish.

The speaker was the principal informant for Éamonn Ó Tuathail's Seanchas Ghleann Ghaibhle, published as a supplement to Béaloideas 4 in 1934. Ó Tuathail says of him that he "speaks Irish fluently", and that he and his brother "continued the practice of speaking Irish to one another when it had become obsolete in the rest of the district." This brother died "some years" before 1931. Ó Tuathail tells us that John Neddy was from Legnagrow, but his paternal grandfather (Ruaidhrí) came from Kinawley, Co Fermanagh.

John Neddy was also visited by others interested in Irish, including Tomás S Mac Cionaoith (originally Skinnader), to collect material.

John Neddy married Maggie Melanophy, on 1880/05/20 according to the parish records. Registered births include Rose (1881), Edward (1883), Ellen (1884-1889), Margaret (1886), Patrick (1888), Bridget (1889), Francis (1891), Ellen (1894), Michael (1896), Mary (1899) and John (1901). The family lived at Legnagrow, and consisted in 1901 of John (50) and Margaret (40), with children Rose (18, a teacher), Maggie (14), Patrick (11), Bridget (9), Francis (7), Helena (5) and Marianne (1). James (60), the speaker's unmarried brother, was nearby, with the speaker's son Michael Maguire (3). In 1911, there was John (62) and Margaret (55), with Patrick (22), Francis (18), Ellen (15), Michael (14), Mary Anne (12) and John (10), and brother James (71) had moved in. The marriage had lasted 30 years, and 10 out of 11 children were living.

John Neddy Maguire died at Legnagrow on 28 July 1938, aged 89. The gravestone reads:
      Sacred heart of Jesus have mercy
      on
      the soul of
      John Maguire
      who died at Legnagrow
      28th July 1938 aged 89 years
      His wife Margaret Maguire
      died 27th June 1934 aged 74 years
      His brother James Maguire
      died 14th March 1929 aged 87 years
      Also his brother Francis Maguire
      who died at Blacklion
      2nd June 1911 aged 56 years
      And his son John Maguire
      who died at Mully
      13th April 1951 aged 49 years
      His son Patrick
      who died 15th Jan 1971
      RIP
      Rose Ann Maguire [wife of Patrick]
      who died 2nd March 1976
      Erected by the family.

There are some subsequent references to John Neddy's relations in the Anglo-Celt: 24/03/1978 p 4, "John's daughter, Mrs Mary Maguire, Mully, and two of his grandsons, John Maguire, Legnagrow, and Frank Maguire, Blacklion," and 29/06/1984 p 23, reporting the death of Blacklion publican, Frank Maguire, "his granduncle [recte, grandfather?] was a native of Legnagrow and was the last native Irish speaker in the area."

Recent references to Seán Éamuinn Ruaidhrí 'ag Uidhir include:
      Colm J O'Boyle, Phonetic texts of East Ulster Irish, MA thesis QUB, 1962, pp 42–7, 47, 50–1, 196–213, 214.
      Heinrich Wagner and Colm Ó Baoill, Linguistic Atlas and Survey of Irish Dialects, Vol IV, 1969, pp 300–3.
      Séamas P Ó Mórdha, "Glangevlin's Irish College", Breifne 8, 1989–91, pp 80–117 and 207–71, at 89–90.
      Nollaig Mac Congáil and Ciarán Ó Duibhín, Glórtha ón tseanaimsir, 2009, pp 48–51, 81.
      Róise Ní Bhaoill, Ulster Gaelic Voices, 2010, pp 298–317.